Expansible anchor

ABSTRACT

An expansible anchor for anchoring in a hole drilled in a component has a shank having a rear end provided with a structure for fixing an article and a front end provided with at least two portions of reduced cross-section with adjoining expander cones, expansible sleeve with a structure including an expansible sleeve positioned over each of the portions of reduced cross-section, at least two convex beads mounted on the expansible sleeve with a structure and projecting radially outwards, each of the beads being provided with at least one opening, and the two portions of reduced cross-section having different diameters.

BACKGROUND OF THE INVENTION

The invention relates to an expansible anchor made of metal foranchoring in a hole drilled in a component.

Expansible anchors of that kind are especially suitable for use in hardbuilding materials; by screwing a nut onto the threaded shank projectingbeyond the component and the article to be fixed, the expander coneintegrally formed with the shank is drawn into the expansible sleevebearing against the wall of the drilled hole. The expansible sleeve isconsequently expanded and becomes wedged in the drilled hole. Theexpansible sleeve is braced in the drilled hole by integrally formedlocking elements, which grip the wall of the drilled hole.

DE PS 41 17 238 discloses an expansible anchor of that kind having twocones over each of which is mounted an expansible sleeve. The expansiblesleeve is provided with tunnel-like, convex beads projecting outwardsthat extend approximately as far as the centre of the expansible sleeve,and also a continuous longitudinal slit and several axially arrangedincisions.

Although that known expansible anchor makes possible slip-freeanchoring, it requires the use of a relatively large amount of energy todrive it in to overcome the resistance to insertion.

Studies have shown that the relatively rigid outer surface of the beadhas an adverse effect on the insertion behaviour of the anchor. Thereason for this is that the outer surface of the bead has two differentregions: a rear region that behaves resiliently during the insertion ofthe anchor and a rigid front region. The rigid region of the beadpresses hard and consequently creates large amounts of friction againstthe concrete and makes it difficult to drive the anchor into the drilledhole.

SUMMARY OF THE INVENTION

The invention is based on the problem of providing an expansible anchorof the kind mentioned at the beginning that can be inserted more easilyand that ensures reliable fixing in the tensile zone of a concrete part.

That problem is solved by an expansible anchor for anchoring in a holedrilled in a component, consisting of a shank which at its rear end hasmeans for fixing an article and at its front end has at least twoportions of reduced cross-section with adjoining expander cones and,positioned over each reduced neck portion, an expansible sleeve on whichare mounted at least two convex beads projecting radially outwards,wherein in accordance with the present invention the beads are providedwith one or more openings, and the diameters of the reduced neckportions are different.

By providing an opening in the bead region, the rigidity of the bead isreduced. In particular, as a result of the reduction in area in therigid region of the bead, the resistance to insertion is reduced and theanchor can be driven in more easily. The opening can have the form of apunched circular bore, giving the bead a tooth-like form. The outer edgeof the bore acts as a locking edge and holds the expansible sleeve inthe drilled hole so that it is immovable in the radial and axialdirections while the expander cone is being drawn in. As a result of thesharp edges biting into the wall of the drilled hole, the expansiblesleeve grips the wall of the drilled hole more strongly and consequentlybecomes fixed.

The sleeve comes to a standstill when torque is applied and the bolt isdrawn into the sleeve.

With anchors of a relatively large diameter it is advantageous toprovide an additional opening in the resilient region of the bead. Therigidity of the bead is thereby reduced still further and the behaviourof the anchor when being driven in is further improved.

As a result of the front neck portion's being thinner than the rear neckportion, in that area the play between the expansible sleeve and theneck is increased. That enables the expansible sleeve to be deformedinwardly more easily and to be better matched to the angle of the cone.That in turn improves the sliding of the expansible sleeve on the coneand ensures uniform good subsequent expansion behaviour in the event ofthe drilled hole becoming wider as a result of cracks forming.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a side view of the expansible anchor according to theinvention,

FIG. 2 shows a section along the line II--II according to FIG. 1,

FIG. 3 shows the expansible anchor according to FIG. 1 inserted in thedrilled hole before torque is applied,

FIG. 4 shows the expansible anchor according to FIG. 3 after torque hasbeen applied,

FIG. 5 shows a plan view of a metal strip, with stamped beads, for themanufacture of the expansible sleeve,

FIG. 6 shows the metal strip according to FIG. 5 in a section along theline X--X, and

FIG. 7 shows a cross-section through the expansible sleeve according toFIG. 6 along the line Y--Y.

DESCRIPTION OF PREFERRED EMBODIMENTS

The expansible anchor illustrated in FIG. 1 consists of a shank 4 havingat its rear end a threaded portion 3 for clamping an article securely.In the front region there are located stepped portions 38, 39, as shownin FIG. 3, adjoining each of which, towards the front end, there arerespective expander cones 1 and 2, having an overlap zone 23. Anexpansible sleeve 11, 12 is mounted in the region of the portion 38, 39.The expansible sleeves 11 and 12 are each manufactured from a metalstrip that has been bent to form a sleeve having a continuous axial slit13. In addition to the slit 13, the expansible sleeves 11 and 12 areprovided with two incisions 34, 35 shown in FIG. 2 which, starting fromthe front edge 16 of the expansible sleeve, extend axially approximatelyas far as the centre of the expansible sleeve.

Two beads 18, 19, shown in FIGS. 1 and 2, extend from the rear edge 17of each expansible sleeve 11 and 12 and project beyond the outer surfaceof the shank portion 4. The beads 18, 19 have one or more openings 10.The openings 10 can have the form of a punched circular bore. The beads18, 19 are thereby given a tooth-like shape with a locking edge 21, asshown in FIG. 7.

The opening 10 is provided in the front region 15 of the beads 18, 19.As insertion aids, the expansible anchor has a first marking 5 and asecond marking 6. FIG. 1 also shows a nut 8 screwed onto the rear end 7of the expansible anchor, and a washer 9.

FIG. 3 shows the expansible anchor disclosed in FIG. 1 after it has beendriven into a cylindrical drilled hole 27, the expansible sleeves 11, 12being shown in longitudinal section through the beads 18, 19. FIG. 3also shows neck portions 31, 32 that merge into the expander cones 1, 2.The diameter of the neck portion 31 is smaller than the diameter of theneck portion 32. FIG. 3 shows how the outer surface of the beads 18, 19makes good contact with the wall of the drilled hole even before theexpansion of the expansible sleeve.

The component 26 to be fixed to the fixing base 25 is pressed againstthe fixing base 25 by means of the nut 8 and the washer 9. By screwingon the nut 8, the expansible sleeves 11, 12 remain in their originalpositions in the drilled hole 27, while the expansible anchor, togetherwith its expander cone 1, 2, is drawn into the expansible sleeves 11, 12by axial displacement, as shown in FIG. 4. As a result of the differentdiameters of the neck portions 31, 32 and the provision of the bore 10in the rigid region 15 of the beads 18, 19, the expansible sleeves 11,12 expand slightly, the outer edge 21 of the bore 10, illustrated inFIGS. 5 and 6, biting into the wall of the drilled hole and bringingabout a stronger gripping of the expansible sleeves 11, 12 in the fixingbase 25.

FIG. 5 illustrates a metal strip having beads 18, 19, bores 10 andincisions 34, 35, from which the expansible sleeves 11, 12 aremanufactured. Instead of a bore 10 in the front region 15 of the bead18, two bores 10, for example, may be provided, as is shown by the bead19. The second bore 10 is provided in the rear region 14 of the bead.

We claim:
 1. An expansible anchor for anchoring in a hole drilled in acomponent, comprising a shank having a rear end provided with means forfixing an article and a front end provided with at least two portions ofreduced cross-section with adjoining expander cones; expansible sleevemeans including an expansible sleeve positioned over each of saidportions of reduced cross-section; at least two convex beads mounted onsaid expansible sleeve means and projecting radially outwards, each ofsaid beads being provided with at least one opening, and said twoportions of reduced cross-section having different diameters.
 2. Anexpansible sleeve as defined in claim 1, wherein said beads have rigidregions in which said openings are provided.
 3. An expansible sleeve asdefined in claim 1, wherein sad openings have the shape of a circularbore.
 4. An expansible sleeve as defined in claim 1, wherein saidopenings form a sharp toothed-shaped edge.
 5. An expansible sleeve asdefined in claim 1, wherein one of said portions of reducedcross-section has a diameter which is smaller than a diameter of theother of said portions of reduced cross-section.